Confocal microscopes are widely used in biology, medical science, pharmaceutical science and the like. Confocal microscopes usually require specimens to be stained, and therefore are not appropriate for observation of living tissues. With confocal microscopes, images can be obtained also from unstained specimens. However, in the case of weakly scattering objects such as biological specimens, confocal transmission microscopes cannot reproduce high contrast images, while confocal reflection microscopes cannot reproduce precise images of the objects.
Nonlinear optical microscopes have been developed as tools that do not require staining specimens before observation. In nonlinear optical microscopes, the second harmonic generation (SHG) signal, the third harmonic generation (THG) signal, the coherent anti-Stokes Raman scattering (CARS) signal or the like is used. Nonlinear optical microscopes, however, are not easy to operate, because they employ a high power pulse laser as a light source.
Phase contrast microscopes, which can convert a phase object into a high contrast irradiance image, are most powerful tools to observe biological specimens. However, they can provide two-dimensional images alone.
Holography can provide three-dimensional images, but resolution is not sufficiently high Microscopy using holography is described in a non-patent document, Etienne Cuche, Pierre Marquet and Christian Depeursinge, “Simultaneous amplitude-contrast and quantitative phase-contrast microscopy by numerical reconstruction of Fresnel off-axis holograms”, Appl. Opt. 38, 6994-7001 (1999), for example.
Optical coherence tomography (OCT) is an exquisite device for biological specimens. However, in OCT, resolution in the depth direction depends on a spectrum width of a light source, and therefore the development of a broadband light source is indispensable in order to gain high resolution in the depth direction.
On the other hand, in industrial applications, there is a need for generating an image of defects inside glass, for example. However, a device which can separately generate a three-dimensional image of refractive index distribution and that of absorptance distribution, has not been developed.
In biology, medical science, pharmaceutical science and the like, there is a need for a microscope which has a high three-dimensional resolution, does not require specimens to be stained and is easy to operate.
Further, in industrial applications, there is a need for a microscope separately generating a three-dimensional image of refractive index distribution and that of absorptance distribution.